I’ve had a standing desk (homemade risers for my work desks) for about a year now, and I’m pretty happy with them. I was already fit, so no change there, but I do find I have better quality sleep, and an easier time relaxing when not standing. I concur, a treadmill would be overkill, and even more troublesome. The standing desks actually make it really easy to collaborate in my office (no chair in the way).